This section describes functions and operators for examining
and manipulating values of type bytea.

SQL defines some string
functions that use key words, rather than commas, to separate
arguments. Details are in Table
9-8. PostgreSQL also
provides versions of these functions that use the regular
function invocation syntax (see Table
9-9).

Table 9-8. SQL
Binary String Functions and Operators

Function

Return Type

Description

Example

Result

string||string

bytea

String concatenation

E'\\\\Post'::bytea ||
E'\\047gres\\000'::bytea

\\Post'gres\000

get_bit(string, offset)

int

Extract bit from string

get_bit(E'Th\\000omas'::bytea,
45)

1

get_byte(string, offset)

int

Extract byte from string

get_byte(E'Th\\000omas'::bytea,
4)

109

octet_length(string)

int

Number of bytes in binary string

octet_length(E'jo\\000se'::bytea)

5

position(substring in string)

int

Location of specified substring

position(E'\\000om'::bytea in
E'Th\\000omas'::bytea)

3

set_bit(string, offset, newvalue)

bytea

Set bit in string

set_bit(E'Th\\000omas'::bytea,
45, 0)

Th\000omAs

set_byte(string, offset, newvalue)

bytea

Set byte in string

set_byte(E'Th\\000omas'::bytea,
4, 64)

Th\000o@as

substring(string [from
int] [for int])

bytea

Extract substring

substring(E'Th\\000omas'::bytea
from 2 for 3)

h\000o

trim([both] bytes
from string)

bytea

Remove the longest string containing only the bytes
in bytes from the start and
end of string

trim(E'\\000'::bytea from
E'\\000Tom\\000'::bytea)

Tom

Additional binary string manipulation functions are available
and are listed in Table
9-9. Some of them are used internally to implement the
SQL-standard string functions
listed in Table
9-8.

Table 9-9. Other Binary String Functions

Function

Return Type

Description

Example

Result

btrim(stringbytea, bytesbytea)

bytea

Remove the longest string consisting only of bytes in
bytes from the start and end
of string

btrim(E'\\000trim\\000'::bytea,
E'\\000'::bytea)

trim

decode(stringtext,
formattext)

bytea

Decode binary data from textual representation in
string. Options for format are same as in encode.